Stabilized ammonium phosphate solutions comprising a galactomannan gum and a metal salt

ABSTRACT

AMMONIUM PHOSPHATE SOLUTIONS THICKENED WITH GALACTO MANNAN GUM ARE STABILIZED WITH REPECT TO VISOSITY BY THE ADDITION OF A MONOR AMOUNT OF A HAVEAY METAL ION SUCH AS CO++, CU++, OR MN++.

3,634,234 STABILIZED AMMONIUM PHOSPHATE SOLU- TIONS COMPRISING AGALACTOMANNAN GUM AND A METAL SALT William W. Morgenthaler, MarylandHeights. Mo., assignor to Monsanto Company, t. Louis, M0. N Drawing.Filed Dec. 15, 1969, Ser. No. 885,354 Int. Cl. A62d 1/00 U.S. Cl. 2527 4Claims ABSTRACT OF THE DISCLOSURE Ammonium phosphate solutions thickenedwith galactomannan gum are stabilized with respect to viscosity by theaddition of a minor amount of a heavy metal ion such as Co++, Cu, orMn++.

BACKGROUND OF THE INVENTION This invention relates to viscositystabilized ammonium phosphate solutions which are used extensively inthe field of fighting fires, particularly forest fires.

It is well known to thicken ammonium phosphate solutions with smallamounts of galactomannan gum to improve its air drop patterns and itsability to stick to surfaces, e.g., trees and bushes with which theycome into contact. See. for instance, US. Pat. 3,223,649 granted Dec.14, 1965. So as to be ready at a moments notice, these thickenedammonium phosphate solutions are made up in advance. However, thesesolutions on prolonged standing often show a serious loss in viscosity.Various stabilizers have been proposed, =e.g., sodium sulfite, zincsulfite, sodium thiosulfate, see US. Pat. 3,146,200, but the amountrequired is impractical.

Therefore it is an object of this invention to provide ammoniumphosphate solutions having improved viscosity stability upon prolongedstanding.

It is a further object to provide improved viscosity solutions withminimal amounts of stabilizers.

Other similar objects of the invention will become apparent to thoseskilled in the art as the invention is further described below.

SUMMARY OF THE INVENTION The viscosity stability of an ammoniumphosphate solution thickened with a galactomannan material is improvedby the addition of a minor, but stabilizing, amount of a transition,i.e., heavy, metal ion.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The ammonium phosphatesolutions in which these transition metal ions perform particularlyeffectively are those that contain at least about 0.5 weight percent,and up to the level at about which the solutions are saturatedtherewith, of dissolved ammonium phosphate salts, including monoammoniumorthophosphate and/or diammonium orthophosphate salts, and alsoincluding the diammonium and monoammonium mixed orthophosphate saltsthat also contain an alkali metal cation, such as monoammonium disodiumorthophosphate, monoammonium dipotassium orthophosphate and the like, nomatter from what source these materials were derived, or in what formthe materials are initially introduced into the aqueous compositions.Generally, it is preferred that the inhibited aqueous phosphatesolutions of this invention have a pH between about 3 and about 9. Whenmonoammonium orthophosphate is the only ammonium phosphate salt presentin the inhibited fire-control compositions of this invention, thepreferred pH of these compositions is generally from about 3 to about 5.Similarly, when diammonium orthophosphate is the only ammonium phosphate3,634,234 Patented Jan. 11, 1972 ice salt contained therein, thepreferred pH is from about 7 to 9. When mixtures of monoammoniumorthophosphate and diammonium orthophosphate are utilized, pHs betweenthese preferred ranges are generally more desirable. However,compositions having pHs somewhat higher or lower than these preferredranges can also be utilized to advantage in the practice of the presentinvention.

The galactomannan materials to which this invention relates arepolysaccharides, generally termed hemicelluloses, and are long chainpolymers of galactose and mannose units. While their exact compositionis not known, they have been found to yield these two sugars onhydrolysis. They are gum-like materials, generally found in plant seeds.Examples of the galactomannans are guar gum, obtained from Cyamopsistetragonolobus (a legume); locust bean gum, obtained from Ceratoniasiliqua; and tara gum, obtained from Cesalpinia spinosa. These materialstypically comprise about 5 to 15% by dry weight of the ammoniumphosphate composition.

The viscosity stabilized ammonium phosphate solutions of the presentinvention can also contain other materials (compounds) withoutdetracting substantially from the benefits that can be obtained bypracticing this invention, for example, the solutions can contain minoramounts of surfactants; inorganic and organic complexing agents such asthe alkali metal tripolyphosphates, pyrophosphates andtrimetaphosphates, as well as the higher polyphosphates such as thehexametaphosphates and also can contain ethylenediamine tetraacetic acidand various alkali metal and ammonium salts thereof and the alkali metaland ammonium nitrilotriacetates; corrosion-inhibiting ingredients; andorganic and inorganic pigments and dyes; as well as many othermaterials.

The viscosity stabilizers of this invention are the transition or heavymetal ions of the fourth and fifth order of the Periodic Table such asvarious zinc, copper, nickel, cobalt, manganese, chromium and cadmiumions. More preferred are the metal ions from the fourth order especiallythose having an atomic number below 30 and particularly preferred arethe ions of metals having odd atomic numbers from 25 to 29 inclusively.These ions are added to the ammonium phosphate solution in an amountfrom about 10 to 70 parts per million (p.p.m.) and preferably from about15 to p.p.m. (This phenomenon is somewhat surprising since these ions inthe foregoing amounts are known to have the reverse effect in otherthickeners such as ca'rboxymethylcellulose which has also been employedas a thickener for ammonium phosphate solutions.) The metal ions areconveniently added to the ammonium phosphate composition as a watersoluble compound having an anion compatible with the composition, e.g.,a chloride or sulfate.

The inhibited phosphate compositions of this invention can bemanufactured via any of a number of manipulative methods, without anynoticeably detrimental effects upon the ultimate performance of thecompositions. For example, the sulfate compound can simply be dissolvedby intermixing it into or with the otherwise completely formulatedaqueous compositions, or at any other stage during the preparation ofthe fire-control composition. Via another method, the sulfate compoundcan first be dissolved in water and the resulting solution thenintermixed subsequently with the ammonium phosphate materials.

Still another process for manufacturing the aqueous stabilized phosphatecompositions described heretofore involves one of the preferredembodiments of the present invention. This preferred embodimentcomprises a concentrate mixture of one or more of the ammonium phosphatesalts described heretofore with one or more of the stabilizer compounds,generally in a particulated,

:olid form. Preferably the compound (s) and ammonium ihosphate salt(s)will be present in this concentrate com- :osition or mixture in amountsproportionate to those 'ound in the fire-control compositions describedhereto- 'ore, so that the final fire-control composition can benanufactured by simply dissolving the concentrate in a ufiicient amountof water. In other words, generally the referred concentratecompositions of this invention will :ontain at least one of theabove-described ammonium )hosphate salts, a galactomannan gum and atleast one )f the stabilizer compounds in a weight range, respecively, offrom about 50.0 to 93.0 percent by weight, 5.0 o 15.0% and 0.05 to 1.50%with the balance being opional materials listed below. It is stillfurther preferred hat these particulated, solid concentrate compositions:ontain a total of at least about 50 weight percent of me or more of theabove-described ammonium phosihate salts. These preferred concentratecompositions can llSO contain effective amounts of practically any otherous air-drops of fire-control compositions, very little weighing andhandling equipment is available that is capable of manufacturing thefire-control compositions from the individual components.

The following examples are included to illustrate the present inventionbut are not to be considered as limiting. Unless otherwise specified allparts are by weight.

EXAMPLE 1 TABLE I.VISCOSITY OF AMMONIUM PHOSPHATE SOLUTIONS CONTAININGCOPPER (II) AS A FUNCTION OF STORAGE TIME Storage time in Weeks 1 Coppercone. on a total solution basis.

2 Percent retained= ngredients desired in the final fire-controlcompositions, .g., dyes, pigments, water-softening agents and the like,.11 of which should preferably be present in the concenrate compositionsin minor amounts, as compared to the vmmonium phosphate salt(s)contained therein. Some of he advantages of these preferred concentratecomposiions can readily be appreciated when it is realized that at mostpoints from which aircraft are loaded for their vari- Current viscosity(cps) Initial viscosity (cps) EXAMPLE 2 An ammonium phosphatefire-control formulation containing a guar gum type thickener (0.9)% wasdissolved in water containing varying amounts of copper, zinc or cadmiumas the viscosity stabilizer. The metal ion was added as the chloridesalt. Test conditions of Example 1 were used. The results are tabulatedin Table II and Table III below.

TABLE II.VISCOSITY OF AMMONIUM PHOSPHATE SOLUTIONS CONTAINING COPPER(II), ZINC (II) AND CADMIUM (II) AS A FUNCTION OF STORAGE TIME Storagetime in weeks Metal and Initial Percent Percent Percent Percent conc.viscosity Ops. ret. Cps. ret Cps. ret. Cps. r

Copper:

1 Metal ion concentration on a total solution basis ppm. 2 Last 2columns 6 and 13 weeks storage.

TABLE IIL-VISCOSITY OF AMMONIUM PHOSPHATE SOLUTIONS CON- TAINING VARIOUSTRANSITION METALS AS A FUNCTION OF TIME Storage time in weeks AdditiveInitial Percent Percent Metal additive (ppm) 1 t'cps.) Ops. ret. Ops.ret

ontrol 1,730 1, 570 91.0 1, 340 77. 5 Chromium (III) 25 1, 720 1, 56090. 7 1, 380 80. 3 50 1, 800 1, 600 89. 0 1, 440 80. 0 Manganese (II) 25l, 850 1, 800 97.3 1, 470 81. 7 50 1, 790 1, 790 100. 0 1, 660 92. 8Cobalt (II) 1, 760 l, 780 101. 2 1, 650 93. 8 5O ,1, 720 1, 720 100. 01, 600 93. 0 Z1110 (II) l, 720 1, 630 94. 8 1, 370 79. 6 50 l, 810 1,690 93. 4 1, 360 75. 2 Nickel (II) 25 1, 740 1, 690 97. 2 1, 450 83. 450 1, 790 1, 690 94. 5 1, 430 80. 0 Copper (II) 25 1, 740 1, 710 98. 31, 620 93. 2 50 l, 870 1, 870 103. 3 1, 860 102. 8

1 Metal ion concentration on a total solution basis.

From the foregoing it will be seen that the degree of viscositystabilization can be tailored to fit the particular requirement bychoice of metal ion with due allowance for the nature of thegalactomannan gum.

The foregoing examples have been described for the purpose ofillustration and not limitation. Many other modifications andramifications will naturally suggest themselves to those skilled in theart based on this disclosure. These are intended to be comprehended aswithin the scope of this invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. An ammonium phosphate solution containing (1) at least 0.5 weightpercent of ammonium phosphate, (2) as a thickening agent a galactomannangum in an amount of from about 5 to 15 weight percent, based on the dryweight of said ammonium phosphate and (3) as a viscosity stabilizer atransition metal salt selected from the group consisting of cobaltchloride, cobalt sulfate, copper chloride, copper sulfate, manganesechloride, manganese sulfate, chromium sulfate, chromium chloride, nickelchloride, nickel sulfate, cadmium chloride and cadmium sulfate, saidsalt being present in an amount to provide from about 10 to about 70ppm. of metal ions.

2. The composition of claim 1 wherein the transition metal salt iscuprous chloride, cuprous sulfate, manganous sulfate, manganouschloride, cobaltus chloride or cobaltus sulfate.

3. A concentrated ammonium phosphate composition useful when diluted anddissolved in Water, said composition comprising at least one ammoniumorthophosphate salt, a galactomannan gum and a transition metal saltselected from the group consisting of copper chloride, copper sulfate,manganese chloride, manganese sulfate, cobalt chloride, cobalt sulfate,chromium sulfate, chromium chloride, nickel sulfate, nickel chloride,cadmium chloride and cadmium sulfate, said respective weight percentsbeing from about 50.0 to about 93.0; about 5 to about 15 and about 0.05to about 1.5.

4. The composition of claim 3 wherein the transition metal salt iscuprous chloride, cuprous sulfate, cobaltus chloride, cobaltus sulfate,manganous sulfate or manganous chloride.

References Cited UNITED STATES PATENTS 3,084,057 4/1963 Jordan 106-2083,146,200 8/ 1964 Goldstein 2528.5-5 3,223,649 12/1965 Langguth 25223,309,324 3/1967 Langguth et al. 2522 3,364,149 1/1968 Morgenthaler 25223,383,307 5/1968 Goetz 2522 JOHN T. GOOLKASIAN, Primary Examiner D. J.FRITSCH, Assistant Examiner U.S. Cl. X.R.

